This thesis studies lesbian detective fiction and specifically considers this genre in its early decades (1980s-1990s) from the United States, United Kingdom, Australia, and New Zealand. This thesis postulates that out of a sample pool of a hundred novels, there are recurring patterns of behaviours and attitudes among the protagonists of this genre within certain physical and metaphorical spaces. These patterns demonstrate a destabilised identity, as the lesbian sleuth never ceases to explore and test the boundaries of her authority as an enforcer of law and order and of her suppressed spatiality as a member of a sexual minority. This causes her to live in a perpetual state of Insider/Outsider liminality and it causes queer trauma to be a fundamental aspect of her character. This thesis considers this concept as the result of long-standing, systemic homophobia and heterosexist normativity, and utilises the notion of queer trauma to interpret the way the lesbian sleuth is inescapably stuck between a sense of duty and justice and a yearning for belonging and self-affirmation. The interpretive process is supported by an extensive and in-depth theoretical research into the fields of history, culture, geography, feminist criticism, gender, and sexuality studies for the selected subject matter. The spaces selected and analysed in this thesis are the queer closet, the medical establishment, domestic settings, and the gay bar. These spaces have been chosen for the significant, emblematic ways in which the lesbian detectives interact with them and have been analysed in order of their importance for the protagonists’ characterisation. The introduction includes introductory statements and the theoretical framework, the first chapter overviews major detectives in the history of crime literature from a spatial perspective; the second chapter discusses the queer closet; the third chapter considers the space of the clinic and the topics of queer trauma and of the pathologisation of homosexuality; the fourth chapter analyses the domestic settings of the protagonists; the fifth chapter examines the context of the gay bar and its history; finally, the conclusion offers closing statements about the focus and originality of this thesis. The originality of this thesis lies in its focus on spaces and on the relationship between the protagonist and society, law and order, and Self and Other. This thesis contributes to the knowledge of queer literature by specifically considering the unescapable liminality of the lesbian/Outsider detective/Insider.